1. Field of the Invention
The present invention relates, in general, to an enclosure having a controlled atmosphere for the continuous treatment of textile yarns deposited on a continuous conveyor belt outside of the enclosure and transported by the conveyor belt through the enclosure. The invention relates more particularly to a sealing head having rollers for the passage of the conveyor belt through the inlet and outlet of the enclosure.
2. Discussion of Background and Relevant Information
The yarns which travel continuously through such an enclosure, in particular through a steaming process enclosure under pressure, are generally deposited in the form of staggered spirals on one or more conveyor belts which circulate horizontally through the enclosure and traverse, at the inlet and at the outlet of the enclosure, sealing heads having rollers which enclose the belt and the yarns so as to prevent a substantial escape of steam.
To perform this function, a known sealing head, illustrated schematically in FIG. 1, includes a body affixed to a wall of the treatment enclosure and carries in a rotating manner a lower stationary roller 2, above which an upper roller 3 is movable in a substantially vertical direction. To this end, the roller 3 rotates on an axis of which each end is mounted in an oscillating bearing 4 at one end of a respective oscillating lever 5 whose other end is journalled at axis 6 on body 1. One or more springs 7 are biased against the lever 5 and are carried by adjustment rods 8 mounted on a frame 9 that can be locked on the body 1. The rods 8 are threaded to permit the adjustment of the compression of the springs 7. The two levers 5 are independently movable with respect to each other, such that the upper roller 3 can be inclined with respect to the roller 2 if the amount of yarn is thicker on one side of the conveyor than the other. The two arms oscillate together if the thickness of the yarn deposited on the conveyor varies, particularly as a function of the density of the deposit of yarn in spirals disposed on the conveyor.
A major disadvantage of this type of device is that the tightening force between the rollers 2 and 3, exerted by the springs, varies with the spacing between the rollers. On the one hand, the rods 8 must be adjusted in length to more or less compress the springs 7 when one wants to deposit yarns having a different density. This requires a manual operation and a careful adjustment in the tension of the springs. On the other hand, when the upper spring 3 must be inclined to allow an asymmetrical deposit to pass, the springs 7 which are more tightly compressed on the side which is raised tend to exert an excessive force which raises the other end of the roller, thus creating a loss of sealing of the enclosure.
Another disadvantage is that a momentary occurrence of an excessive tightening force can disturb the deposit of yarn. Finally, each time that one wishes to release the pressure of the springs to raise the upper roller, a manual operation is necessary to unlock and tilt the frame 9.